Electronic throttle control ETC has been applied to automotive vehicles in which an electrical signal indicating an accelerator position, such as an accelerator pedal displacement away from a rest position, is provided to a powertrain controller which generates powertrain control commands in response to the signal. The powertrain control commands include fueling commands to control engine output torque, transmission shift commands, and EGR, turbocharger wastegate, and glow plug commands.
The powertrain control authority of the accelerator may, at times during powertrain operation, be superseded or augmented by specialized control algorithms. For example, when the accelerator is not depressed away from its rest position and the engine is operating, an idle speed control may be given such control authority. Such authority may gradually be reduced as the accelerator is depressed. Alternatively, a cruise control algorithm may be given such authority when activated by the powertrain operator. Still further, authority given a traction control algorithm may supersede that of a depressed accelerator under certain operating conditions. The specialized control algorithms having authority generally command an powertrain operating level to which the powertrain is responsive.
By depressing the accelerator, the powertrain operator may regain any lost powertrain control authority. However, until such time as accelerator command exceeds the powertrain operating level commanded by any specialized algorithm that may have authority, the accelerator will, under known prior art control approaches, appear to the operator to have limited authority or indeed no authority at all, as the accelerator movement will appear to have little or no impact on the powertrain operating level. For example, until the engine output torque commanded by the accelerator position exceeds that of an idle speed control algorithm that may be operating, movement of that accelerator will not produce a proportionate change in engine torque. Such limited authority may not please the powertrain operator, as it may make the powertrain feel less responsive and may make the operator feel less in control of the powertrain.
Accordingly, what is needed is a powertrain control approach that provides for an interface between any specialized powertrain control algorithms that may, at times, have authority over the powertrain, and the accelerator, to allow for a cooperation between the algorithms and the accelerator whereby the specialized algorithms may carry out their specialized tasks without significantly diminishing the apparent authority of the accelerator.